The VIC-20 actually has 5 KB of RAM but 1.5 KB of that is used by zero page, the stack, the OS KERNAL and BASIC, leaving 3.5 KB of RAM for BASIC or binary programs. The VIC-20 can be expanded up to 40 KB of RAM but 8 KB of that is not contiguous resulting in a maximum of 28,159 bytes free in BASIC.